tailieunhanh - Chapter 012. Pain: Pathophysiology and Management

Since different diseases produce characteristic patterns of tissue damage, the quality, time course, and location of a patient's pain complaint and the location of tenderness provide important diagnostic clues and are used to evaluate the response to treatment. Once this information is obtained, it is the obligation of the physician to provide rapid and effective pain relief. The Pain Sensory System Pain is an unpleasant sensation localized to a part of the body. | Chapter 012. Pain Pathophysiology and Management Since different diseases produce characteristic patterns of tissue damage the quality time course and location of a patient s pain complaint and the location of tenderness provide important diagnostic clues and are used to evaluate the response to treatment. Once this information is obtained it is the obligation of the physician to provide rapid and effective pain relief. The Pain Sensory System Pain is an unpleasant sensation localized to a part of the body. It is often described in terms of a penetrating or tissue-destructive process . stabbing burning twisting tearing squeezing and or of a bodily or emotional reaction . terrifying nauseating sickening . Furthermore any pain of moderate or higher intensity is accompanied by anxiety and the urge to escape or terminate the feeling. These properties illustrate the duality of pain it is both sensation and emotion. When acute pain is characteristically associated with behavioral arousal and a stress response consisting of increased blood pressure heart rate pupil diameter and plasma cortisol levels. In addition local muscle contraction . limb flexion abdominal wall rigidity is often present. Peripheral Mechanisms The Primary Afferent Nociceptor A peripheral nerve consists of the axons of three different types of neurons primary sensory afferents motor neurons and sympathetic postganglionic neurons Fig. 12-1 . The cell bodies of primary sensory afferents are located in the dorsal root ganglia in the vertebral foramina. The primary afferent axon bifurcates to send one process into the spinal cord and the other to innervate tissues. Primary afferents are classified by their diameter degree of myelination and conduction velocity. The largest-diameter fibers A-beta A0 respond maximally to light touch and or moving stimuli they are present primarily in nerves that innervate the skin. In normal individuals the activity of these fibers does not produce pain. There are